underling vs assistant

underling and assistant both are nouns.

Word	Noun	Adjective	Verb	Adverb
underling	Yes	No	No	No
assistant	Yes	Yes	No	No

As nouns, assistant is a hypernym of underling; that is, assistant is a word with a broader meaning than underling:

underling: an assistant subject to the authority or control of another
assistant: a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

Other hypernyms of underling include help, helper, supporter.

underling (noun)	assistant (noun)
an assistant subject to the authority or control of another	a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

underling (adjective)	assistant (adjective)
	of or relating to a person who is subordinate to another